Robinson, in his Essay towards a natural History of Westmoreland and Cumberland states, that, at first, the country people round Keswick marked their sheep with black-lead. Afterwards, they discovered the art of employing it in their earthenware, and also to preserve iron from rust. The same writer says, the Dutch use it in dyeing, to render black more durable; and that they buy it in large quantities for that purpose. But their application of it for dyeing, we should consider as highly questionable. The mode of eradicating black-lead by means of an elastic gum, called caoutchouc, or, Indian-rubber, was, we have been informed, first discovered in England somewhere about sixty years ago. COLOURED GLASS. The manufacture of glass we find was quite common in Ethiopia, Syria, Assyria, and other Eastern countries, in the earliest ages of the world, as Diodorus Siculus informs us, who says, the Ethiopians enclosed in glass, the bodies of their parents and friends; we doubt, however, that on this point, the historian was deceived. But it really appears probable that soon after the art of making glass was discovered, the idea of communicating to it some colours would easily present itself. This probability appears increased, when it is recollected that much care is requisite to render glass perfectly colourless. As the various metallic particles with which stone and sand abound, (these being the chief ingredients of which glass is composed, and which gradually give tints in fusion,) will almost unavoidably communicate some hue or other, therefore the perfection of glass is to have it perfectly colourless. But with respect to coloured glass; so frequently have people been imposed upon by having coloured glass sold to them for valuable stones, that some conscientious authors have very laudably and carefully abstained from lending the benefit of instruction in its manufacture, by publishing the method. The Egyptian artists were so famous in the manufacture of glass, that the Romans were content to receive this article from the glass-houses in Alexandria, and did not interfere in endeavouring to procure the art themselves, until the latter part of the empire. We read that an Egyptian priest made a present to the Emperor Adrian of several beautiful glass cups, which sparkled with many colours; and such value did that august personage place upon these toys, that he ordered them to be used only on high feasts and solemnities.